UG 



BALLOON OBSERVATION 
and INSTRUCTIONS 



on the sobfect of 



WORK IN THE BASKET 



i 



tsaued by the 

Divi»on of Military Aeronautics 

U. S. Army 



^ A free (raotlatioii of thu iitiic!i booklet 
" lastroctlooB »a sajet dDT(a^«ii en Nacelle,** 
and an added diacooTM on Balloon ObBerTationa 



{.'' '.. 



WASHrNGTON 

GOVERNMENT PRINTING OFnCE 

AUGUST, 1918 




Book^.A5 

• R 1 r 



BALLOON OBSERVATION 
and INSTRUCTIONS 

on the subject of 

WORK IN THE BASKET 



Issued by the 1 

U , X . '\jj'CL\ dit|T Division of Military Aeronautics 
U. S. Army 



^ A free translation of the French booklet 
"Instructions au sujet du Travail en Nacelle," 
and an added discourse on Balloon Observations 



^1^ 



WASHINGTON 

GOVERNMENT PRINTING OFFICE 

AUGUST, 1918 



1^, I ?' 



LIBRARY OF CONGRESS 

APR291921 

DOCUMENTS DIVISION 



^ PART I. 



f- BALLOON OBSERVATION. 

INTRODUCTORY NOTE. 

In this pamphlet will be laid down the general prin- 
ciples and also the limitations which govern obser- 
vation from balloons. Balloon observation includes 
more than actual artillery observation. (See ' ^ Employ- 
ment of Balloons.") 

The details of cooperation between balloons and 
artillery are issued from time to time by the General 
Staff in the form of pamphlets. ,;TOiatever the system 
ordered at the time, there are certain principles which 
do not change. 

In artillery observation it can not be emphasized too 
strongly that success-depends Jb.oth-On^ 

1. The efficiency of the balloon observers, including 
an intimate knowledge of the ground within view. 

2. An intimate knowledge by artillery commanders 
of the possibilities and limitations of balloon obser- 
vation. 

The limitations of balloon observation are — 

1 . Distance from the target. 

2. Height of observer. 

3. Visibility. 

Distance from the target is inevitable, but can be 
lessened by advanced positions and winch tracks. 

83144-18 (3) 



During active operation it has sometimes 'been possi- 
ble to approach balloons within 4,500 meters (4,921 
yards) of the line. 

The low height of the balloon compared with an 
aeroplane is a drawback, as it brings a question of 
dead ground and exaggerated perspective. 

Visibility is the determining factor of the balloon's 
usefulness. In very high winds, very misty or cloudy 
weather, observation is impossible, and owing to its 
stationary nature the balloon can not, by any special 
effort on the part of its observers, overcome unfavor- 
able conditions in the same way as is possible in the 
case of aeroplane observation. 

On the other hand, a balloon flying at a height of 
1,500 meters (1,640 yards) and 7,000 meters (7,651 
yards) from the line, under favorable weather condi- 
tions, combines in a marked degree many of the ad- 
vantages of air and ground observation. 

In the first place, glasses can be used. Secondly, 
the balloon observer can converse direct with the 
battery commander by telephone. Apart, therefore, 
from ease and certainty in reporting observations, the- 
telephone system enables an elastic program of work to 
be drawn up and admits of personal conversation be- 
tween the battery commander and the observer, 
often permitting mistakes or misunderstandings to be 
cleared up during shoot instead of afterwards. 

Finally, owing to the continuous nature of his ob- 
servation from the same spot, the balloon observer is 
able to learn his country in the greatest detail and 
can keep a close watch on suspected roads or areas of 
country. ^ 



LIAISON BETWEEN BALLOONS AND ARTILLERY. 

The work of balloons is principally with the artillery, 
and close liaison between these two branches is indis- 
pensable if the best results are to be obtained. This 
close liaison should be promoted on the following lines : 

(a) Balloon companies should each, as far as possi- 
ble, be allotted specific artillery organizations. This 
facilitates telephone communication, prevents dupli- 
cation of liaison work, and leads to a far more intimate 
and personal liaison than does any other method. 

(b) Balloon observers must visit batteries frequent- 
ly, and sometimes be attached for short periods. 
Shoots should be discussed, especially if unsuccessful. 
Observers should prepare and take with them when 
visiting batteries a list of targets which are clearly 
visible from the balloon and on which they can ob- 
serve effectively. Similarly, artillery commanders 
should let balloon observers know of any further tar- 
gets which they especially wish to engage, as work 
previously prepared on the ground saves time and 
gives better results. 

(c) Artillery officers should visit the balloon and 
make ascents. They will thus become acquainted 
with the extent of view from the balloon and the 
ability and difficulties of the observers. 

EMPLOYMENT OF BALLOONS. 

In view of the above, the work most suitable for 
balloons is as follows: 

GENERAL SURVEYANCE OF ENEMY'S ACTIVmES. 

(a) Reporting modifications of enemy defensive or- 
ganization; detecting movements of convoys and 



6 

trains. Their importance and itineraries, locating 
infantry signals, and all other activities such as re- 
vealed hy fires, smokes, dust, trails, etc. 

(b) Spotting active hostile batteries and reporting 
hostile shelling. Reporting hostile shelling is a duty 
for which balloons are especially suitable, as they are 
favorably situated to observe both the flash of the 
gun and the fall of the shell. From this information 
it is possible to direct not only neutralizing fire on the 
hostile battery, but often also to establish the caliber 
of the guns and the arc of fire of the battery. 

RANGING AND ADJUSTING OF FIRE. 

(a) Observing fire for destruction on all targets, 
counterbattery, or bombardment. 

(b) Reporting fleeting targets and observing fire on 
them. 

(c) Observing for registration fire. 

(d) Observing fire on the enemy's communications. 

(e) Cooperation with aeroplanes. 



PART II. 



WORK IN THE BASKET. 

[Translation of French document, "Instructions au sujet du Travail en Nacelle," 
, a publication of French G. Q. G., 1918, by Lieut. Kellogg.] 

The rapidity and precision of the work in the basket 
depend not only on the natural gifts of the observer, 
but also very largely on his methods of work. 

The object of the following instructions is to tell 
the student observers the general methods they should 
follow and to explain the use of these methods. 

The principal operations which they must be able 
to execute rapidly are as follows: 

1. Orientation and general reconnaissance of the 
terrain. 

2. Spotting points on the ground seen on the map 
and points on the map seen on the ground. 

3. Observation of fire. 

Chapter 1. 

ORIENTATION AND GENERAL RECONNAISSANCE OF THE 
TERRAIN. 

This is the operation which the observer executes 
on his first ascension in a new sector; this is how it 
should be conducted. 

1. Rapidly hole over ilie terrain around the ascensional 
point in order to orient the map. 

This is done by finding in some direction from the 
ascensional point a line giving an easily identified 

(7) 



8 

direction (a road, an edge of woods, etc.). Orient 
the map so as to make this Hne on the map parallel 
to the line on the ground. 

The map can also be oriented by means of the 
compass. 

2. Locate the horizontal lyrojeciion of the halloon. 

The observer may know already the winch position, 
but the balloon is carried off horizontally from the 
winch sometimes as much as 400 or 500 meters (436 
to 545 yards). Thus it is essential not to confuse the 
winch position with the horizontal projection of the 
balloon. If this is done, errors will be made in the 
operations which we are going to discuss later, where 
we make use of this known point. 

It is pretty hard to materialize definitely the ver- 
tical line passing through the basket. The effect of 
the wind and the movements of the balloon make it 
impossible to use a plumb line. The observer has to 
find his projection on the ground by leaning first 
from one side of the basket and then from the other 
in order to diminish the chances of error. An ap- 
proximation of 25 or 50 meters is sufficiently accurate 
for the general reconnaissance which it is necessary 
to make. 

3. Leaving the region beneath the halloon, acquaint 
yourself, step hy step, with the most prominent points 
in different direciions — masses of woods, villages, etc. 

There are two methods — by the process of chem- 
inement or tracing landmarks and by the process of 
direct alisfnment. 



9 

The process of "cheminement" or tracing consists 
in following outlines, such as roads, streams, or hedges, 
identifying as you go along details of the terrain 
which these lines pass through or near. On account 
of the deformations due to the effect of perspective and 
to the unevenness of the ground, and particularly on 
account of the deformation of angles, if it is a winding 
road, this method often leads to errors; it should be 
employed only in certain cases defined below: 

The process of **direct alignment" consists of 
studying the terrain by following successive directions 
from the baloon position. 

We call the '' alignment" of a point the trace, on the 
terrain, of the vertical plane passing through this 
point and through the eye of the observer; in per- 
spective vision, when the observer determines the 
point in question, this alignment would appear to 
him a vertical line. On the map it is nothing more 
than the straight line joining the point under considera- 
tion to the vertical projection of the balloon. 

The method of alignment, then, consists in first 
identifying the most prominent points near the balloon 
and finding, by cheminement or tracing, the lines 
running from these points. A point found directly 
by cheminement should not be considered as 
definitely determined until its alignment has 
been verified. 

This first reconnaissance is not to study the terrain 
in all its details, but only to fix in the memory a 
certain number of prominent points scattered through- 
out the sector in order to facilitate later work. 

83144—18 2 



10 

These points should be very distinct, visible to the 
naked eye, and of characteristic forms, so that there 
will be no danger of confusing them with others — 
masses of woods, important villages, etc. Roads with 
borders of trees, large paths for hauUng supplies, 
when taken together, are very valuable for quickly 
finding others. 

Chapter II. 
SPOTTING OF POINTS. 

Generalities. — In all spotting operations, whether 
working from the map to the terrain or vice versa, the 
difficulty is due to the fact that the situation of the 
point has to be found on a two-dimension surface. 

The best method of work wiU be, then, that which 
suppresses as quickly as possible one of these dimen- 
sion's and to conduct the research on a straight line. 

Any point can be placed on the terrain or on the 
map if you know the following elements: 

1. Its ''direction" or alignment. 

2. Its situation on this alignment — that is, its 
•''range." 

In oblique vision, a digression in direction is always 
much more apparent than a digression of the same 
size in range. Thus the direction of a point can 
be identified with more facility and precision 
than its range. For these reasons, the following 
methods consider two distinct phases in all spotting 
operations: 

1. Investigation of direction. 

2. Investigation of range. 



11 

The investigation in direction always comes 
first, as it is easier, and its result makes the inves- 
tigation for range easier. 

LOCATING ON THE GROUND AN OBJECT SEEN ON THE 

MAPS. 

If it is a question of a very visible point (cross-roads, 
an isolated house, a corner of woods, etc.), the spotting 
can be done almost immediately, it was found in the 
general reconnaissance of the terrain, which was dis- 
cussed in chapter 1. 

If, on the contrary, the point under consideration is 
difficult to find (a piece of trench in a confused and 
cut-up region, a battery emplacement, etc.), w^e must 
have recourse to a precise method. 

1. KESEARCH IN DIRECTION. 

Join on the map the projection of the baUoon and 
the center of the objective. Identify this direction on 
the terrain by finding on the alignment a prominent 
point. This line can be drawn in the basket. It is a 
good thing to draw tlie alignment on a vertical 
photograph of the objective also, in order to 
have a greater number of reference points than 
the map could give. 

2. INVESTIGATION OF RANGE. 

Identify on the map (or photo) two points, one 
situated over and one short of the objective. Narrow 
down this bracket step by step until the object is 
recognized. 



12 

As this investigation of the range is the more diffi- 
cult, observers must be warned against certain methods 
which are to be absolutely avoided — 

1. Never identify the range of a point by com- 
paring it with tliat of a near-by point situated on 
a different alignment. 

If these two points are not at exactly the same 
height, the deformations due to oblique vision can 
falsify their apparent relative range. The point 
farthest away can even seem nearer, and the nearest 
point farther away. 

Example (fig. 1). — Suppose there are two trees, A 
and B, A being nearer the balloon and higher than B. 
It can happen that, in oblique vision (fig. 2), B having 
its image B' and A its image A', the depression of the 
image B' is more than that of A'. In this case, the 
observer will be tempted to believe that the tree B is 
nearer him than the tree A. 

2. All oblique alignment in investigating the 
range must be absolutely avoided. 

Oblique alignment means a line connecting two 
points on the map and not passing tlirough the hori- 
zontal projection of the balloon. 

You might be tempted to use an alignment to find 
the range of an objective after having determined the 
direction. The process would consist in finding on the 
map two points so placed that the straight line be- 
tween them passes through the objective, visualizing 
this line on the terrain, and placing the objective at the 
intersection of this visualized line and the direct align- 
ment. This result, which would be accurate if the 
ground were absolutely flat, is made erroneous by the 



14 



unevenness of the terrain. On account of this, the 
oblique ahgnment does not pass, in obhque vision, 
through the same points as its horizontal projection 
on the map. 




Fi$.3 



Example (fig. 3). — On the map C is the objective, 
A and B two points so situated that the line AB passes 
through C, and EF the direct alignment, or the line 
balloon objective. The line AB coincided on the ter- 
rain, with the trace of the vertical plane passing 



15 



through A and B. In obUque vision (fig. 4) it is differ- 
ent. The fine A'C'B' is a curve which follows the 




irregularities of the ground, and the point C is not on 
the oblique alignment A'B'. 

LOCATING ON THE MAP AN OBJECT SEEN ON THE 
GROUND. 

1. Determine -first on the map the approximate 
region where the objective is seen. 

A result which you can obtain very quickly, thanks 
to the points which you had found in your first recon- 
naissance of the terrain. 



16 

2. Investigation of direction. 

This operation consists in determining the align- 
ment of the objective. As this ahgnment is a straight 
line, you only have to know two points. One of them 
could be the horizontal projection of the balloon; but 
you must realize that this position is always changing 
a little, and it is hard to determine it with absolute 
precision. It is better to carr}^ on the operation inde- 
pendent of this position, which means applying the 
following method: 

Choose on the alignment of the center of the 
objective two points, one over and one short? 
and easily identifiable on the map. Draw with 
a pencil in the region of tlie objective the align- 
ment thus obtained. These points should be, 
as far as possible, precise details of the terrain, 
such as a corner of woods, an angle of a house, a 
place where roads or trenches cross, an isolated tree, 
etc. When the alignment of the objective does not 
pass through any such points, the difficulty can be 
overcome by determining in what proportions it cuts 
a known element, such as an edge of woods or a hedge, 
provided this element is plainly perpendicular 
to the direction of observation. 

This direction can be approximated to the extent of 
the thickness of the pencil mark. On its accuracy the 
final result depends. The difficulty lies in materializ- 
ing the alignment — that is, the vertical line through 
the center of the objective — in order to lessen the 
chances for mistakes. Student observers should have 
frequent practice in this exercise. 



17 

When the point to be found is near the edge of the 
map it is sometnnes necessary to take both reference 
points between the balloon and the objective; this 
should be avoided as much as possible, because it is 
apt to be less exact than when the objective is brack- 
eted by its reference points. 

Thus (fig. 5), two reference points A and B deter- 
mine the ahgnment AB, O, the objective, is situated 
at some point between A and B. An error AA' in the 
spotting of one of these points leads to a smaller error 
in the position of the objective 00' — that is, smaller 
than AA'. 

On the other hand, let both the reference points 
''a" and '^b" (fig. 6) be situated short of the objective 
O, '^ a" being nearer the objective and ''b" nearer to the 
balloon. An error aa' in spotting ^^a" leads to an 
error 00' in the o])jective greater than aa'. Notice 
that this error diminishes as '^A" approaches O, thus 
''a'' being as a^, the error a^a'^ equal to aa' leads to 
an error OO'i, in the objective, less than 00'. We 
would thus obtain an analogous result if we would 
move the point '^b" farther away. 

Therefore, when you are obliged to take the two 
reference points between you and tlie objective, 
choose one as near the objective as possible and 
the other as near as possible to the balloon. 

3. Investigation of range. 

Identify details of the terrain situated over and 
short of the objective on the alignment. Narrow this 
bracket down step by step; situate the objective on 
the map according to its relative distance from the 



18 

two nearest identifiable reference points, taking into 
account the (ieformations due to the laws of perspective 
and the relief of the ground. 




If you have a vertical photograph of the region, 
trace the alignment on this photograph and make the 
investigation in range b}^ the same means. 



19 

The dangers against which I warned you before in 
connection with the investigation of range apply in 
this case also, so it is unnecessary to repeat them. 

When the two last identifiable reference points are 
some distance from each other, the situation of the 
objective has a possible error, of which you know the 
size according to the distance between the two refer- 
ence points; it might be interesting to remember this 
in case different information is obtained on this objec- 
tive from that obtained in the balloon. 

This error can be considerably diminished if you 
use a vertical photograph; the investigation can then 
be carried on by the same method as on the map, with 
greater precision. In the case of a battery, particu- 
larly, it is for the observer to find the position of each 
piece. 

In case, on account of dead ground or of a mask 
before the battery, the observer sees the fiashes or 
the smoke without seeing the battery itself, he should 
mark the exact alignment in which the flashes or 
smoke are seen, and determine the bracket in range — 
that is, the reference points nearest the objective 
which are clearly over and short. This document 
compared with other information can facilitate the 
identification of the battery. 

Chapter III. 

OBSERVATION OF FIRE. 

The observation of fire is essentially the following 
operation, repeated for each shot or salvo: Locating 
on the ground the position of one point, which is the 



20 

point of burst, and announcing its situation in refer- 
ence to another point, which is the target. 

But it has been demonstrated that it is impossible, 
without using the map, to determine the error in 
range of one point relatively to another point not on 
the same alignment. 

The operation must consist in : 

1. Spotting on the map the point of burst. 

2. Reading its position in reference to the target. 
The observation of the burst — that is, the spotting 

of the point of impact — is the same whether the 
observation is direct or lateral. 

1. PREPARATION OF THE FIRE. 

Draw on the map, and copy if possible on a 
vertical photograph, the line balloon target 
(alignment of the center of the objective) and 
draw through this point a perpendicular to the 
alignment. In case the observation is lateral, 
draw also the line battery target and its perpen- 
dicular. 

To draw the line balloon target, it is not necessary 
to know the horizontal projection of the balloon. It 
is enough to find . on the ground a point situated 
directly on the alignment of the center of the objective. 

2. OBSERVATION OF A SHOT. 

When the shell bursts, take quickly an align- 
ment and reference points in range of the point 
of burst; spot this point on the map or on the 
photograph; give its error in reference to the line 
battery-target, measuring it by the scale on the 



21 

map or on the photograph. (It is well to put the 
graphic scale on the photos.) 

The deUcate part of the operation consists in seeing 
the shot at the moment of burst. One must try to 
spot the apex of the inverted cone formed by the 
burst, without paying any attention to the more or 
less considerable cloud of smoke which follows and 
which will cause mistakes if the burst was not seen 
immediately. The method of situating the point is 
the same as that described above. 

For the direction, one reference point is enough, 
because one can consider the alignment of the point 
as practically parallel to the balloon-target. For the 
range, a rapid study of the terrain before the fu-e is 
sufficient to allow the observer to know the reference 
points by which he can guide himself. His eyes 
must never leave the point of burst until he has 
j&xed well in his mind its situation in reference to 
appropriate reference points. Not to do this would 
lead to erroi-s and to loss of time while he has to find 
the point again with his glasses to study it some 
more. 

When the observation is direct, the direction of the 
burst is, of course, known as soon as it is seen. When 
the observation is lateral, it is well to remember that 
the line battery-target can not be materialized on the 
ground because it is in reality an oblique alignmentj 
leading to the same errors which we have discussed. 
It foUows all irregularities of the ground and, on 
account of this, can not be followed exactly in oblique 
vision. 



22 • 

Particularly around batteries, the ground is often 
very irregular. There may even be little spaces of 
dead ground, caused by hollows which the map does 
not always show. The above method, applied with 
the help of photographs, allows you to avoid errors 
resulting from the existence of these hidden parts. 

PRACTICAL ADVICE. 

1 . WorJc sitting down, with the map on your Icnees and 
leaning against the edge of the hasJcet. 

This position is preferable to all others, because it 
allows the observer — 

(a) To correct with his head and shoulders the 
movements of the basket. 

(b) To have the map always before him. He can 
consult it at any moment, mark the necessary align- 
ments without loss of time, use it as a desk for draw- 
ing or taking notes, or as a wind shield when looking 
at photographs. 

The observer who works standing up must either 
pick up his map from the bottom of the basket every 
time he needs it, which is out of the question, or fasten 
it outside the basket; the latter solution is inadvisable, 
it necessitates working in the wind when the map is 
referred to, and every time the observer turns to look 
at his map he disturbs the equilibrium of the basket. 

It is advisable to work standing up only on days 
when there is practically no wind, and the balloon is 
continually turning and never becomes oriented. 



23 

2. Have ahvays within reacJi aflat rule, o 'pencil^ and 
a duodecitneter rule. 

To be able to trace an alignment on the map with 
precision, the rule must rest on a firm surface. This 
happens when the map is mounted on a cL-awmg 
board; when it is mounted on a frame with rollers, the 
frame should have, between the two thicknesses of 
the map, a board level with the edges of the frame on 
which the rule can slirle with its whole length on the 
map. 

With a hard pencil, well sharpened, precise and neat 
alignments can be drawn. 

The duodecimeter rule is for measuring distances on 
photographs and on the map; chiefly in observations 
of fire. 

3. Hold tke fi.eld glasses with both hands. 

This advice, sometimes ignored by observers with- 
out expedience, has a great influence on the accuracy 
of information. When an observer holds the glasses 
in one hand, it is much more difficult for him to cor- 
rect the movements caused by the balloon and to con- 
centrate on a point. It is very important, therefore, 
to hold the glasses fi/mly with both hands, especially 
when you are making a delicate observation or when 
you wish to study an "objective'' in detail. 



PAET III. 
APPENDIX. 

Note 1. — All observations of rounds refer to the 
line battery target (b-t) and a line perpendicular to 
same passing through the target. Observations are 
given in meters right and left and whether the round 
is over or short. Indications as to deflection are given 
before those of range. Indications as to the amount 
of error precede those as to the sense of the error. 
Example, 50 meters ''Right/' ''over." Owing to the 
dispersion of fire when adjusting fire for field artillery 
or howitzer, it is unnecessary and of little value to 
the battery to give the amount of the error in range 
except when asked for by the battery commander or 
when the error in range is abnormal (over 200 meters). 

When the target is clearly visible and the effect of 
a round hitting a target is evident, the observation 
''Target'^ is reported. Unless the observer is certain 
of having seen the bursts "Unobserved" will be sent. 
If, however, after a few seconds smoke can be seen 
rising from trees, houses, etc., in proximity to the 
target, the observation "Unobserved, but smoke, seen 
rising left and over," may be given. 

Note 2. — Observers must beware of being over- 
confident in their own powers of observation. True 
confidence only comes with experience, and this is 
best attained by making ascents with a trained ob- 

(25) 



26 

server when ranging a battery and checking one's own 
observations with those given by him. An observa- 
tion must never be given unless the observer is quite 
certain as to its correctness. It is essential to good 
results that the artillery may be able to rely abso- 
lutely on the observations sent down. The observer 
must watch the target but must avoid straining his 
eyes by putting up his glasses as soon as a round is 
fired. He should arrange for the chart room to 
inform him when a shell is about to fall. The latter 
must know the time of flight. Observers must learn 
to distinguish readily the bursts of different kinds of 
shells. 

Note 3. — If the balloon-target line makes an angle 
with the battery-target line of more than 30° with 
field artillery and 20° with heavy, the balloon posi- 
tion will be given to the battery, and all observations 
will be given with reference to the balloon-target line 
and the battery will replot accordingly. 



